[Effect of free-air CO2 enrichment on biomass accumulation and distribution in rice]

Investigation on the effect of free-air CO2 enrichment (FACE) on biomass accumulation and distribution in different parts of rice plant treated with 200 mumol.mol-1 CO2 elevation under field condition showed that the dry matter accumulated from transplanting to 20th day after heading and the total biomass increased significantly, while the dry mater accumulated from 20th day after heading to maturity was significantly depressed under FACE treatment. The enhancement of both leaf area index (LAI) and net assimilation rate (NAR) under FACE treatment resulted in the increase of dry matter accumulated from transplanting to heading, while the dominant reason for the increase of dry matter accumulated during 20 days after heading was the slowed decline of LAI. The decline of dry matter accumulated from 20th day to maturity was mainly caused by the decrease of NAR. The percentage of dry matter distributed in stem and sheath increased under FACE treatment, while that in leaf decreased, and that in panicle showed no significant change. The content (%) and amount of soluble sugar and starch in stem and sheath at heading was significantly elevated under FACE. The grain yield of rice under FACE treatment could be significantly improved by raising biomass.